Step 1

Mix the dry ingredients in a large bowl. Add melted butter, vinegar, and water. Mix until just combined. This batter will be thin. Pour into a 9x13 pan that has been sprayed with cooking sprayed.

Step 2

Bake in a preheated 325 degree oven for 35 to 45 minutes. Cool completely.

Step 3

Beat the butter and marshmallow cream in the bowl of an electric mixer fitted with the paddle attachment, for 2 minutes. Reduce speed to low, and slowly add the powdered sugar, 1 cup at a time until well incorporated. Add the salt, vanilla, and heavy cream. Beat until combined.

Step 4

Crush the Oreos with a rolling pin. I like to leave some big chunks, I like having big pieces in the frosting. Fold into the frosting. Spread frosting over cooled cake.